The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Additive Manufacturing (“AM”), also referred to as 3D printing, is a manufacturing technique in which material is added sequentially, layer by layer, in order to build a part. This is in contrast to traditional machining, where the part starts as a block of material that is then whittled down to the final desired shape. With AM fabrication, a directed power source is used to agglomerate material (typically powder) into a final, near net-shape article. Three dimensional articles are manufactured one layer at a time as an assemblage of two-dimensional sections. One important advantage of AM fabrication is that complex shapes (e.g. parts with internal features) can be realized. Another important advantage is that the material required is limited to that used to form the final part. Thus, AM fabrication has the benefit of very little material loss. This is especially important for expensive/tightly controlled materials.
The use of AM for metal fabrication is relatively recent. Historically, plastics have been the focus of commercial systems that employ AM. Nevertheless, the use of metals with AM is highly commercially and technologically important because the majority of engineered structures rely heavily on metals. Metal AM requires a relatively high power, highly focused laser beam (typically on the order of 100 W-1000 W) to melt, fuse, and/or sinter metallic powder. The metal powder is typically placed in a powder bed during the AM process. The laser beam is rastered along the powder surface to make a two-dimensional section per pass. Once each layer is completed, the powder bed retracts and new powder is layered on top of the just-completed layer. Considering that a typical layer thickness is only about 50-100 microns, it can be seen how this rastering is the most time consuming step. This is the principal reason why objects that would only take two to three hours to machine using traditional machining methods may take up to eight hours or more using AM. Moreover, due to the necessity of rastering the laser beam, the maximum part size can be limited. Presently a 25 cm×25 cm area part size is the largest part size that can be made with an AM technique that involves rastering the laser beam. Accordingly, there is a strong desire to reduce the time required to manufacture objects, and particularly metal objects, using AM. One important challenge that the present disclosure addresses is overcoming this relatively slow speed necessitated by the raster scanning operation employed with a conventional AM fabrication process.